my fans only turn on when i turn the a/c on. is it the fan switch causing that? and is the fan switch on passenger side on the 350 engine?
I could use some help.

 

Okay. The fan if u have duals. The one fan will turn on if you have a/c on. the other one will only turn on when the engine gets hot by the fan switch. That could be the colprit if the secondary fan not working.

 

Pull the lead off the switch and ground it with the ignition in 'run'. If the fan comes on you'll know the relay and wiring are good. The fan switch itself is unlikely to go bad. It may just not be getting hot enough.

 

yea thats what its supposed to do. but when i turn the a/c on they both kick on. even when i just start the car

 

It's probably the fan relay thats bad. Usually if the fans work only when you turn on the a/c its because it bypasses the relay. If the relay is bad they wont turn on, only when u run the a/c.

 

There's a relay for each fan if you have duals. The AC switch, temp switch and ECM all provide a ground to relay to engage the fan(s).

 

The primary fan turns on at 220°F. The secondary turn on temp is 238°F

That is true for '87 and older. '88-up both fans should run with the A/C.

The a/c pressure switch also uses the relay to make the (secondary) fan operate. It and the fan switch are tied together and switch to ground. If the relay is bad, the fan will not work at all, a/c or not.